UWSP Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the UWSP Observatory clear sky chart from 2005-11-06 to 2024-12-09.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	14% 9% 3 8% 5% 4 5% 4 5% 7% 37%	101841
	Night	14% 10% 4 8% 5% 4 4 4 5% 6% 38%	98050
Transparency	Day	45% 6% 12% 25% 12% 1	105333
	Night	45% 6% 11% 23% 13% 1	102685
Seeing	Day	17% 11% 30% 26% 13% 4	16095
	Night	17% 10% 31% 31% 11% 1	26003

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	12% 15% 7% 14% 6% 4 4 3 4 5% 26%	2527
	11th to 20th	Day	9% 13% 5% 15% 7% 6% 8% 7% 6% 5% 18%	2530
	21st to end	Day	14% 18% 7% 15% 6% 5% 4 3 4 5% 20%	2847
February	1st to 10th	Day	9% 12% 6% 9% 5% 5% 5% 4 5% 7% 32%	1710
	11th to 20th	Day	11% 11% 3 8% 6% 4 5% 4 6% 7% 35%	1744
	21st to end	Day	11% 12% 4 11% 5% 5% 5% 4 4 8% 30%	1570
March	1st to 10th	Day	12% 10% 3 5% 3 3 3 2 4 6% 48%	3120
	11th to 20th	Day	9% 8% 4 9% 5% 5% 4 3 5% 8% 40%	3371
	21st to end	Day	21% 12% 3 10% 4 4 4 3 4 5% 29%	4115
April	1st to 10th	Day	16% 13% 4 8% 5% 4 5% 3 5% 7% 31%	2280
	11th to 20th	Day	20% 10% 3 7% 5% 4 4 3 5% 5% 33%	2254
	21st to end	Day	19% 11% 3 7% 5% 5% 5% 4 4 6% 32%	2370
May	1st to 10th	Day	16% 7% 3 6% 5% 4 5% 3 6% 7% 39%	4332
	11th to 20th	Day	15% 6% 2 6% 4 4 3 3 5% 8% 45%	4399
	21st to end	Day	15% 7% 2 8% 5% 4 5% 4 5% 6% 38%	4824
June	1st to 10th	Day	13% 6% 1 5% 5% 4 4 3 5% 9% 44%	2660
	11th to 20th	Day	15% 6% 2 7% 5% 4 5% 4 6% 8% 38%	2660
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 4 7% 9% 40%	2660
July	1st to 10th	Day	13% 5% 2 7% 5% 5% 6% 5% 7% 10% 38%	4440
	11th to 20th	Day	6% 2 1 4 4 5% 5% 5% 7% 10% 51%	4440
	21st to end	Day	9% 5% 2 7% 4 5% 5% 5% 6% 8% 45%	4813
August	1st to 10th	Day	11% 6% 2 7% 4 5% 6% 4 6% 8% 41%	4423
	11th to 20th	Day	14% 5% 2 5% 4 4 5% 3 6% 8% 46%	3901
	21st to end	Day	13% 6% 2 8% 4 4 5% 4 5% 8% 41%	4180
September	1st to 10th	Day	15% 6% 2 5% 4 4 4 4 6% 6% 45%	2280
	11th to 20th	Day	13% 5% 2 6% 3 5% 4 4 5% 7% 46%	2230
	21st to end	Day	14% 7% 2 7% 3 5% 4 4 6% 7% 40%	2090
October	1st to 10th	Day	14% 7% 2 7% 4 4 3 4 5% 7% 43%	1917
	11th to 20th	Day	18% 13% 3 7% 4 4 4 3 4 7% 32%	1900
	21st to end	Day	17% 11% 4 7% 4 3 3 4 4 6% 36%	1895
November	1st to 10th	Day	15% 10% 3 5% 5% 3 3 3 5% 7% 41%	1762
	11th to 20th	Day	14% 13% 4 10% 6% 5% 4 4 5% 5% 29%	1712
	21st to end	Day	15% 11% 4 9% 5% 5% 4 3 5% 6% 34%	1600
December	1st to 10th	Day	12% 13% 4 11% 7% 5% 6% 4 5% 5% 28%	1584
	11th to 20th	Day	12% 15% 6% 11% 6% 6% 5% 4 5% 6% 25%	1918
	21st to end	Day	20% 21% 7% 12% 5% 4 3 3 4 3 18%	2783
January	1st to 10th	Night	12% 15% 7% 12% 5% 4 3 2 3 4 32%	4428
	11th to 20th	Night	10% 13% 5% 15% 7% 6% 7% 6% 6% 5% 20%	4440
	21st to end	Night	13% 19% 9% 11% 5% 5% 5% 3 4 5% 21%	4819
February	1st to 10th	Night	8% 13% 5% 11% 6% 5% 3 4 6% 5% 34%	2470
	11th to 20th	Night	9% 9% 4 8% 5% 6% 6% 4 4 6% 39%	2322
	21st to end	Night	16% 11% 4 9% 6% 4 4 4 4 5% 33%	1884
March	1st to 10th	Night	12% 8% 2 6% 4 4 4 4 5% 7% 46%	3733
	11th to 20th	Night	10% 8% 3 9% 5% 5% 5% 4 5% 6% 40%	3618
	21st to end	Night	22% 10% 3 11% 5% 4 4 3 4 5% 29%	3515
April	1st to 10th	Night	19% 11% 3 7% 5% 4 3 3 5% 5% 36%	1900
	11th to 20th	Night	21% 7% 3 6% 4 3 4 3 6% 5% 37%	1875
	21st to end	Night	18% 9% 2 7% 4 4 5% 4 5% 6% 37%	1809
May	1st to 10th	Night	17% 8% 3 7% 4 4 4 4 5% 7% 36%	2567
	11th to 20th	Night	12% 5% 2 6% 4 4 4 4 6% 7% 46%	2506
	21st to end	Night	15% 7% 3 7% 5% 4 4 3 5% 6% 41%	2743
June	1st to 10th	Night	11% 5% 3 5% 4 5% 5% 4 6% 8% 45%	1520
	11th to 20th	Night	12% 6% 2 7% 5% 4 4 4 6% 8% 41%	1520
	21st to end	Night	11% 5% 2 5% 5% 4 4 4 5% 7% 48%	1520
July	1st to 10th	Night	15% 4 2 5% 5% 4 4 4 6% 8% 43%	2530
	11th to 20th	Night	5% 3 2 3 3 4 4 4 7% 8% 56%	2530
	21st to end	Night	8% 5% 2 6% 4 4 3 4 5% 8% 51%	2750
August	1st to 10th	Night	11% 5% 2 6% 4 4 4 3 5% 7% 48%	2517
	11th to 20th	Night	11% 6% 2 5% 4 4 4 3 5% 7% 48%	2931
	21st to end	Night	12% 5% 2 5% 4 4 4 4 6% 6% 47%	3476
September	1st to 10th	Night	10% 5% 2 4 3 3 4 3 5% 7% 54%	1900
	11th to 20th	Night	12% 5% 1 4 3 3 4 3 5% 7% 53%	1930
	21st to end	Night	13% 6% 2 5% 3 3 4 3 4 7% 49%	2090
October	1st to 10th	Night	12% 6% 3 5% 3 3 5% 3 5% 7% 49%	2261
	11th to 20th	Night	15% 8% 3 7% 4 4 4 4 5% 7% 39%	2280
	21st to end	Night	17% 12% 3 7% 4 5% 4 4 4 6% 34%	2703
November	1st to 10th	Night	15% 9% 3 6% 3 4 3 3 5% 5% 43%	2536
	11th to 20th	Night	14% 13% 4 9% 5% 5% 5% 3 4 5% 34%	2685
	21st to end	Night	14% 13% 4 9% 5% 4 4 3 4 5% 34%	2800
December	1st to 10th	Night	12% 12% 4 11% 5% 5% 5% 4 5% 7% 31%	2779
	11th to 20th	Night	12% 15% 6% 11% 6% 4 5% 3 4 5% 28%	3279
	21st to end	Night	24% 16% 5% 10% 4 4 3 3 3 4 22%	4884

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	60% 6% 11% 17% 6% 1	2528
	11th to 20th	Day	62% 9% 10% 14% 5% 1	2530
	21st to end	Day	65% 5% 12% 13% 4	2847
February	1st to 10th	Day	50% 5% 14% 18% 11% 1	1710
	11th to 20th	Day	47% 7% 12% 23% 10% 1	1753
	21st to end	Day	52% 7% 12% 18% 9% 2	1570
March	1st to 10th	Day	38% 5% 12% 24% 19% 2	3120
	11th to 20th	Day	40% 6% 14% 24% 14% 2	3371
	21st to end	Day	57% 6% 9% 20% 7% 1	4115
April	1st to 10th	Day	52% 7% 10% 19% 11% 1	2280
	11th to 20th	Day	52% 6% 8% 21% 12% 2	2254
	21st to end	Day	52% 7% 10% 18% 11% 1	2370
May	1st to 10th	Day	41% 9% 11% 26% 13%	4372
	11th to 20th	Day	37% 6% 12% 32% 13% 1	4403
	21st to end	Day	45% 7% 10% 21% 15% 1	4837
June	1st to 10th	Day	36% 7% 14% 28% 14% 1	2660
	11th to 20th	Day	42% 7% 13% 25% 13% 1	2660
	21st to end	Day	39% 8% 15% 26% 12% 1	2660
July	1st to 10th	Day	41% 5% 17% 27% 8% 1	4371
	11th to 20th	Day	26% 6% 16% 35% 16% 2	4365
	21st to end	Day	37% 5% 12% 25% 19% 1	4662
August	1st to 10th	Day	41% 5% 14% 26% 12% 1	4408
	11th to 20th	Day	37% 5% 11% 34% 13%	3940
	21st to end	Day	42% 3 13% 29% 11% 1	4179
September	1st to 10th	Day	38% 6% 13% 26% 16% 1	2280
	11th to 20th	Day	36% 7% 16% 31% 9% 1	2230
	21st to end	Day	41% 7% 13% 27% 12%	2090
October	1st to 10th	Day	27% 4 8% 39% 22%	3177
	11th to 20th	Day	44% 4 10% 26% 15% 1	3140
	21st to end	Day	45% 3 13% 29% 10%	3095
November	1st to 10th	Day	43% 6% 13% 23% 14% 1	1762
	11th to 20th	Day	56% 5% 11% 19% 9% 1	1712
	21st to end	Day	52% 5% 15% 22% 6% 1	1600
December	1st to 10th	Day	57% 6% 12% 20% 5% 1	1584
	11th to 20th	Day	57% 7% 14% 13% 7% 2	1915
	21st to end	Day	70% 6% 7% 12% 5%	2783
January	1st to 10th	Night	56% 5% 9% 21% 8% 1	4428
	11th to 20th	Night	61% 8% 10% 14% 6%	4440
	21st to end	Night	64% 7% 9% 15% 5%	4819
February	1st to 10th	Night	51% 5% 10% 21% 11% 1	2470
	11th to 20th	Night	44% 8% 11% 24% 11% 2	2323
	21st to end	Night	52% 6% 11% 19% 9% 2	1884
March	1st to 10th	Night	38% 6% 13% 27% 12% 3	3733
	11th to 20th	Night	42% 7% 10% 24% 16% 1	3618
	21st to end	Night	57% 7% 7% 19% 9% 1	3515
April	1st to 10th	Night	50% 6% 8% 18% 17% 1	1900
	11th to 20th	Night	46% 6% 10% 21% 14% 3	1875
	21st to end	Night	45% 8% 12% 20% 14% 2	1809
May	1st to 10th	Night	46% 8% 14% 15% 17%	2592
	11th to 20th	Night	33% 8% 12% 29% 16% 2	2507
	21st to end	Night	41% 8% 12% 20% 18% 1	2751
June	1st to 10th	Night	33% 10% 14% 26% 16% 1	1520
	11th to 20th	Night	39% 7% 14% 24% 15% 2	1520
	21st to end	Night	34% 6% 15% 29% 13% 3	1520
July	1st to 10th	Night	39% 4 18% 22% 13% 3	2490
	11th to 20th	Night	25% 5% 16% 33% 19% 2	2482
	21st to end	Night	32% 5% 12% 26% 22% 2	2662
August	1st to 10th	Night	36% 5% 12% 29% 16% 1	2508
	11th to 20th	Night	36% 6% 12% 30% 15% 1	2958
	21st to end	Night	37% 4 14% 24% 19% 2	3476
September	1st to 10th	Night	30% 7% 12% 31% 20% 1	1900
	11th to 20th	Night	32% 6% 13% 34% 15% 1	1930
	21st to end	Night	36% 6% 13% 30% 15% 1	2090
October	1st to 10th	Night	27% 4 7% 37% 23% 3	3768
	11th to 20th	Night	34% 4 10% 33% 18% 1	3779
	21st to end	Night	49% 3 9% 23% 15%	4453
November	1st to 10th	Night	42% 5% 13% 24% 14% 1	2536
	11th to 20th	Night	53% 6% 12% 17% 12% 1	2685
	21st to end	Night	51% 5% 14% 23% 6% 1	2800
December	1st to 10th	Night	53% 6% 14% 20% 6%	2779
	11th to 20th	Night	58% 6% 11% 18% 6% 1	3281
	21st to end	Night	65% 6% 8% 15% 5%	4884

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	16% 14% 31% 26% 10% 2	270
	11th to 20th	Day	19% 13% 39% 21% 7% 1	270
	21st to end	Day	22% 10% 33% 29% 5%	297
February	1st to 10th	Day	14% 17% 39% 22% 7% 2	270
	11th to 20th	Day	17% 21% 35% 18% 8%	270
	21st to end	Day	18% 16% 44% 20% 1	225
March	1st to 10th	Day	19% 13% 41% 20% 6%	270
	11th to 20th	Day	22% 14% 32% 22% 9% 2	270
	21st to end	Day	27% 12% 30% 22% 7% 1	469
April	1st to 10th	Day	26% 15% 30% 25% 3	460
	11th to 20th	Day	29% 13% 27% 19% 10% 2	452
	21st to end	Day	20% 14% 33% 20% 11% 2	460
May	1st to 10th	Day	21% 13% 32% 26% 8% 1	611
	11th to 20th	Day	20% 11% 30% 24% 12% 3	675
	21st to end	Day	19% 9% 27% 26% 13% 5%	734
June	1st to 10th	Day	12% 9% 29% 30% 15% 6%	680
	11th to 20th	Day	18% 8% 30% 27% 14% 4	680
	21st to end	Day	15% 8% 29% 30% 14% 5%	680
July	1st to 10th	Day	8% 3 21% 32% 26% 10%	671
	11th to 20th	Day	8% 6% 26% 34% 17% 9%	668
	21st to end	Day	7% 4 26% 32% 23% 8%	739
August	1st to 10th	Day	11% 5% 23% 30% 22% 8%	676
	11th to 20th	Day	13% 5% 21% 26% 25% 10%	581
	21st to end	Day	15% 6% 21% 29% 21% 7%	539
September	1st to 10th	Day	16% 8% 23% 28% 18% 7%	490
	11th to 20th	Day	13% 6% 21% 36% 19% 5%	490
	21st to end	Day	17% 10% 26% 26% 16% 4	490
October	1st to 10th	Day	15% 14% 28% 24% 15% 4	317
	11th to 20th	Day	24% 15% 35% 19% 7%	300
	21st to end	Day	23% 16% 36% 20% 3 2	330
November	1st to 10th	Day	19% 15% 36% 20% 9% 1	300
	11th to 20th	Day	18% 20% 36% 21% 5%	300
	21st to end	Day	22% 16% 41% 15% 7%	300
December	1st to 10th	Day	17% 15% 43% 18% 7%	294
	11th to 20th	Day	18% 20% 38% 19% 5% 1	270
	21st to end	Day	28% 18% 34% 15% 4	297
January	1st to 10th	Night	17% 12% 38% 26% 6% 1	950
	11th to 20th	Night	19% 12% 35% 27% 6% 1	950
	21st to end	Night	19% 9% 37% 29% 7%	1045
February	1st to 10th	Night	14% 12% 37% 30% 6% 1	950
	11th to 20th	Night	15% 13% 38% 26% 7%	848
	21st to end	Night	21% 15% 35% 25% 4	628
March	1st to 10th	Night	17% 14% 33% 28% 8% 1	760
	11th to 20th	Night	18% 12% 36% 25% 9%	656
	21st to end	Night	20% 11% 28% 31% 8% 2	627
April	1st to 10th	Night	23% 11% 35% 24% 6%	570
	11th to 20th	Night	23% 10% 32% 29% 6%	563
	21st to end	Night	22% 10% 32% 29% 6% 1	570
May	1st to 10th	Night	22% 9% 35% 28% 6% 1	570
	11th to 20th	Night	19% 9% 31% 31% 9% 1	561
	21st to end	Night	15% 6% 23% 41% 15%	617
June	1st to 10th	Night	13% 6% 28% 39% 13% 1	570
	11th to 20th	Night	14% 5% 32% 36% 12% 1	570
	21st to end	Night	11% 5% 24% 44% 15% 1	570
July	1st to 10th	Night	9% 2 19% 44% 24% 2	555
	11th to 20th	Night	8% 4 22% 42% 21% 3	552
	21st to end	Night	7% 3 19% 46% 23% 2	624
August	1st to 10th	Night	9% 2 17% 46% 23% 2	567
	11th to 20th	Night	11% 3 18% 36% 28% 4	564
	21st to end	Night	14% 3 19% 42% 19% 3	627
September	1st to 10th	Night	12% 4 24% 38% 17% 5%	570
	11th to 20th	Night	13% 4 26% 34% 19% 3	600
	21st to end	Night	15% 7% 24% 36% 16% 1	760
October	1st to 10th	Night	15% 9% 26% 30% 19% 1	760
	11th to 20th	Night	18% 12% 33% 30% 7%	760
	21st to end	Night	23% 12% 31% 26% 8%	836
November	1st to 10th	Night	19% 10% 37% 26% 8% 1	780
	11th to 20th	Night	20% 15% 36% 22% 7%	885
	21st to end	Night	21% 15% 35% 23% 6%	1000
December	1st to 10th	Night	19% 11% 39% 24% 6%	993
	11th to 20th	Night	21% 14% 34% 25% 6% 1	950
	21st to end	Night	27% 13% 33% 23% 4	1045

Page generated at 2024-12-06 02:54:49. Version ac07

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